U.S. Pat. No. 5,162,445, which is commonly assigned with the present application, discloses a phase transfer polymer modification process in which a polymer of an isoolefin and a para-alkyl styrene, is functionalized at a plurality of pendant sites by introducing a plurality of random electrophilic halo-benzylic sites. The copolymer is now reactive with nucleophilic reagents that displace the halogens and introduce new functional groups such as vinyl ester groups and/or phenyl ether groups. Since the polymer and the nucleophilic reagent are not soluble in a common reaction medium, the reaction requires the use of two liquid solvent phases which are at least partially miscible, and a phase transfer catalyst which is soluble in the same liquid phase as the nucleophilic reagent and forms a complex therewith which is soluble in the other liquid phase. The complex transfers into the other liquid phase where the nucleophilic reagent displaces halogen ions and replaces them with the desired pendant functionality, e.g., ester or ether groups.
Among the problems encountered with phase transfer processes is the high cost of phase transfer catalysts, the environmental problems caused by the discharge of chemical-containing process waste streams, and the problems involved in attempting to recover the phase transfer catalyst from the two phase reaction medium.
U.S. Pat. No. 4,754,089 discloses a phase transfer reaction process for the production of agricultural chemicals, pharmaceuticals and other specialty chemicals. The patent discloses an aqueous phase containing a first reactant and a phase transfer catalyst capable of complexing therewith isolated by means of a membrane present within the reactor from an immiscible organic liquid phase containing a second reactant which is soluble therein. The reactant-catalyst complex is capable of passing into or through the membrane to the organic liquid phase where the reactants react to release the phase transfer catalyst which returns to the first phase to complex with more of the first reactant and transfer it into or through the membrane to repeat the reaction cycle until either or both of the reactants are used up. Such membrane reactors are expensive and the reaction rate is reduced by the separation of the phases. However, such liquid phase separation does enable the recovery of the expensive phase transfer catalyst, after the reaction is completed, since the catalyst is isolated within the phase in which it is soluble, such as water.
It is desirable to be able to recover the expensive phase transfer catalyst from a conventional two phase integrated liquid-liquid reaction system, which does not require the use of a membrane reactor, and in which one of the liquids must be a non-polar liquid, such as a cycloalkane, in order to function as a good solvent for both the starting second reactant, such as a hydrocarbon-paramethyl styrene copolymer, and for the reaction product, as the copolymer is provided with additional pendant functional groups during the reaction. In such a system the other liquid cannot be pure water since water is completely immiscible with non-polar liquids, such as cycloalkanes, no phase integration occurs, and the reaction rate is very slow and unsatisfactory.
In conventional two phase integrated liquid-liquid reaction systems using polar and non-polar liquids which have the necessary degree of miscibility, the phase transfer catalyst remaining, after the reaction is completed, is contained within the waste effluent comprising miscible amounts of the polar and non-polar liquids and is lost.